SEARCH · USGS Science

Results for “Aquaculture”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

USGS2020

Atlantic salmon (Salmo salar) exposed to different preparatory photoperiods during smoltification show varying responses in gill Na+/K+-ATPase, salinity-specific mRNA transcription and ionocyte differentiation

Control of the parr-smolt transformation (or smoltification) is crucial for the husbandry and successful seawater (SW) transfer of Atlantic salmon ( Salmo salar ) reared in freshwater (FW) hatcheries. Photoperiod is an important environmental signal that initiates the complex physiological, morphological and behavioural changes that coincide with marine migration. While the use of long-day photoperiods to initiate smoltification has been well studied, this study investigated how three preparatory photoperiods in FW (LD 08:16, LD 12:12, LD 16:08) preceding exposure to 24-h light (LD 24:0) may influence or enhance smolt performance and growth post-SW transfer. After the photoperiod treatment phase (8 weeks), all groups were exposed to LD 24:0 for 8 weeks (FW) and then transferred to SW for a further 8 weeks. Exposure to LD 16:08 induced rapid development of smolt-related characteristics such as increased gill NKA activity, gill NKAα1b mRNA, and plasma cortisol, and decreased gill NKAα1a mRNA levels and condition factor through the 8-week treatment phase. Subsequent exposure to a LD 24:0 photoperiod resulted in a partial reversal of several of these characteristics, suggesting these fish went through a partial desmoltification. Exposure to LD 12:12 for 8 weeks prior to LD 24:0 elicited an intermediary response in smoltification attributes compared to LD 16:08 and LD 08:16. The LD 12:12 group adapted to SW and showed no negative effects on growth or physiological responses after transfer to SW. Exposure to a shortened photoperiod (LD 08:16) did not elicit any smoltification-related changes prior to LD 24:0, however, exposure to LD 24:0 increased gill NKA activity, plasma cortisol, changes in NKAα1a and NKAα1b mRNA, and the ratio of NKAα1b: NKAα1a. These results were confirmed by the expected changes in NKAα1a and NKAα 1b-positive immuno-reactive gill ionocytes. In summary, after exposure to LD 24:0 fish in the LD 08:16 group showed similar levels of change to those of the LD 16:08 group during the initial FW phase (prior to exposure to LD 24:0). After SW transfer, all groups were able to upregulate SW-specific NKAα1b mRNA and acclimate to SW, even though no increase in cortisol was evident. By the end of the study, there was no difference in SW growth among the groups. Overall, our data indicate that LD 16:08 advanced hypoosmoregulatory characteristics prior to LD 24:0 exposure. In addition, the physiological and molecular indicators measured in this group suggest that fish could have been transferred to SW immediately after 8 weeks in LD 16:08, with no added benefit of successive exposure to LD 24:0, which is typically used by industry to induce smoltification.

Aquaculture↗

USGS2021

Production of haploid gynogens to inform genomic resource development in the paleotetraploid pallid sturgeon (Scaphirhynchus albus)

Order Acipenseriformes (sturgeons and paddlefishes) is an ancient lineage of osteichthyan fishes (>200 million years old) with most extant species at conservation risk. A relatively basal species, the pallid sturgeon, Scaphirhynchus albus, is a federally endangered species native to the Mississippi and Missouri River basins. Hybridization with sympatric shovelnose sturgeon, S. platorynchus, is one of several threats to pallid sturgeon. Current molecular markers cannot reliably distinguish among pure species and multigenerational backcrosses. This information is critical for implementation of management strategies to increase populations through natural reproduction and artificial propagation. Genotypes from a large panel of unlinked single-nucleotide polymorphisms (SNPs) may provide greater resolution of the two species; however, paralogous sequence variants (PSVs) within individuals resulting from an ancient whole genome duplication event confound SNP development. The aim of this study was to produce pallid sturgeon gynogens that contain 100% homozygous DNA contributed by only the maternal parent and have enough DNA for future SNP marker development. When homozygous gynogens are sequenced, heterozygosity at a locus within an individual indicates the presence of incorrectly aligned sequences that contain PSVs; accurate identification of these multi-locus contigs can facilitate their exclusion when developing disomic markers. In this study, we attempted to produce two types of pallid sturgeon gynogens: a) haploid gynogens produced from the activation of pallid sturgeon eggs with ultraviolet-irradiated sperm from the distantly related paddlefish (Polyodon spathula), and b) doubled haploids produced from the activation of pallid sturgeon eggs with irradiated paddlefish milt followed by thermal shock to suppress the first mitotic division. Production of doubled haploids, gynogens with 100% homozygous DNA and double the genome content of haploid gynogens, was pursued because it was originally unknown if haploid gyongens would survive long enough to attain enough genetic material for SNP marker development. We performed flow cytometry and microsatellite genotyping on the specimens in order to confirm haploid and doubled haploid status. Our study was unable to successfully yield doubled haploids; however, we successfully produced haploid gynogens that contained enough nuclear DNA for our future SNP marker development study. Interestingly, this study also produced paddlefish × pallid sturgeon hybrids in the control groups in two separate years; this is the first study to report viable offspring between the paddlefish and a Scaphirhynchus sturgeon species and reflects on the malleability of the genomes of the species in this order.

Louisiana, Arkansas, Missouri, Nebraska, North Dak↗

USGS2024

Effect of florfenicol administered through feed on Atlantic salmon (Salmo salar) gut and its microbiome

Although concerns about the impacts of antibiotics in aquatic organisms are reported worldwide, the potential adverse effects on fish gut microbial communities and fish health are still not well known. In this study, we investigated the effects of florfenicol (FFC) on the gut microbiome and gastrointestinal (GIT) gene expression in juvenile Atlantic salmon ( Salmo salar ). Three doses of FFC were used to coat experimental feed at 10, 20 and 30 mg/kg/ fish body weight (bw). The feed was administered for 18 days, followed by a 10-day recovery period. The metatranscriptome analysis revealed that 10 and 30 mg/kg bw of FFC led to the downregulation of genes involved in the transcription of NADH-ubiquinone oxidoreductase chain-1, suggesting that the antibiotic targets bacterial respiratory metabolism. The 30 mg/kg bw FFC treatment upregulated genes that encode glycolytic enzymes, such as phosphoglycerate kinase, indicating a disruption of energy metabolism in the microbiome. Analysis of the fish host transcriptome showed that the FFC treatment affected cellular processes in the GIT system of fish, including pathways related to apoptosis and DNA metabolism. The 30 mg/kg bw FFC treatment specifically activated pathways related to cellular regulation, including LXR/RXR activation, FXR/RXR activation, and protein ubiquitination. At the end of the recovery phase, the 30 mg/kg bw FFC treated group altered pathways related to EIF2 signaling and lysine degradation.

Aquaculture↗

USGS2024

Rates of osmoconformation in triploid eastern oysters, and comparison to their diploid half-siblings

Triploid eastern oysters ( Crassostrea virginica ) suffer greater mortalities than diploids in the U.S. Gulf of Mexico estuaries when extreme low salinities (< 5) and elevated temperatures (≥ 28 °C) coincide. To investigate potential causes, changes in plasma osmolality, hemolymph pH, valve opening and mortality in diploid and triploid oyster half-siblings were compared during a step-down gradual acclimation from a salinity of 5 to 1 (5, 2.5, 2.0, 1.5, 1.0) at 23 °C (expt 1) and at 28 °C (expt 2). To further explore differences in diploid and triploid oyster responses to changing salinity, we compared their plasma osmolality after abrupt decreases in salinity from 20 to 10 and 5, followed by increases in salinity from 5 and 10 to 20 once oysters had osmoconformed to the lowered salinities (expt 3). Lastly, changes in wet weights of mantle tissue explants were compared between diploid and triploid oysters every 10 min for 40 min after being transferred from a salinity of 20 to 10 (expt 4). Oysters of both ploidies were able to osmoconform to water at salinities between 5 and 1.5. After a decrease in salinity, triploid oysters were slower to open their valves and osmoconform, were less efficient in maintaining acid-base status enduring longer periods of acidic hemolymph pH, and were less efficient in regulating tissue water content compared to half-sibling diploid oysters. At a salinity of 1.0, plasma of both diploid and triploid oysters remained hyperosmotic, their hemolymph acidic and their valves closed. Oysters osmoconformed faster at 28 °C than at 23 °C, but the combination of low salinity (≤ 1.5) and higher temperature caused rapid mortalities regardless of ploidies. Triploid oysters, however, started dying earlier and at greater percentages when salinity of 1.5 and temperature of 28 °C were combined. Triploids have been embraced as a means to support higher production, but results indicate superimposed stressors, such as low salinity and high temperature, may be more lethal to triploid than diploid oysters.

Aquaculture↗

USGS2004

Feasibility of measuring dissolved carbon dioxide based on head space partial pressures

We describe an instrument prototype that measures dissolved carbon dioxide (DC) without need for standard wetted probe membranes or titration. DC is calculated using Henry's Law, water temperature, and the steady-state partial pressure of carbon dioxide that develops within the instrument's vertical gas-liquid contacting chamber. Gas-phase partial pressures were determined with either an infrared detector (ID) or by measuring voltage developed by a pH electrode immersed in an isolated sodium carbonate solution (SC) sparged with recirculated head space gas. Calculated DC concentrations were compared with those obtained by titration over a range of DC (2, 4, 8, 12, 16, 20, 24, and 28mg/l), total alkalinity (35, 120, and 250mg/l as CaCO3), total dissolved gas pressure (-178 to 120 mmHg), and dissolved oxygen concentrations (7, 14, and 18 mg/l). Statistically significant (P < 0.001) correlations were established between head space (ID) and titrimetrically determined DC concentrations (R2 = 0.987-0.999, N = 96). Millivolt and titrimetric values from the SC solution tests were also correlated (P < 0.001, R 2 = 0.997, N = 16). The absolute and relative error associated with the use of the ID and SC solution averaged 0.9mg/l DC and 7.0% and 0.6 mg/l DC and 9.6%, respectively. The precision of DC estimates established in a second test series was good; coefficients of variation (100(SD/mean)) for the head space (ID) and titration analyses were 0.99% and 1.7%. Precision of the SC solution method was 1.3%. In a third test series, a single ID was coupled with four replicate head space units so as to permit sequential monitoring (15 min intervals) of a common water source. Here, appropriate gas samples were secured using a series of solenoid valves (1.6 mm bore) activated by a time-based controller. This system configuration reduced the capital cost per sample site from US$ 2695 to 876. Absolute error averaged 2.9, 3.1, 3.7, and 2.7 mg/ l for replicates 1-4 (N = 36) during a 21-day test period (DC range, 36-40 mg/l). The ID meter was then modified so as to provide for DO as well as DC measurements across components of an intensive fish production system. ?? 2003 Elsevier B.V. All rights reserved.

Aquacultural Engineering↗

USGS2006

Limestone fluidized bed treatment of acid-impacted water at the Craig Brook National Fish Hatchery, Maine, USA

Decades of atmospheric acid deposition have resulted in widespread lake and river acidification in the northeastern U.S. Biological effects of acidification include increased mortality of sensitive aquatic species such as the endangered Atlantic salmon (Salmo salar). The purpose of this paper is to describe the development of a limestone-based fluidized bed system for the treatment of acid-impacted waters. The treatment system was tested at the Craig Brook National Fish Hatchery in East Orland, Maine over a period of 3 years. The product water from the treatment system was diluted with hatchery water to prepare water supplies with three different levels of alkalinity for testing of fish health and survival. Based on positive results from a prototype system used in the first year of the study, a larger demonstration system was used in the second and third years with the objective of decreasing operating costs. Carbon dioxide was used to accelerate limestone dissolution, and was the major factor in system performance, as evidenced by the model result: Alk = 72.84 ?? P(CO2)1/2; R2 = 0.975. No significant acidic incursions were noted for the control water over the course of the study. Had these incursions occurred, survivability in the untreated water would likely have been much more severely impacted. Treated water consistently provided elevated alkalinity and pH above that of the hatchery source water. ?? 2005 Elsevier B.V. All rights reserved.

Aquacultural Engineering↗

USGS2007

Use of avoidance response by rainbow trout to carbon dioxide for fish self-transfer between tanks

Convenient, economical, and reduced labor fish harvest and transfer systems are required to realize operating cost savings that can be achieved with the use of much larger and deeper circular culture tanks. To achieve these goals, we developed a new technology for transferring fish based on their avoidance behavior to elevated concentrations of dissolved carbon dioxide (CO2). We observed this behavioral response during controlled, replicated experiments that showed dissolved CO2 concentrations of 60-120 mg/L induced rainbow trout (Oncorhynchus mykiss) to swim out of their 11 m3 "growout" tank, through a transfer pipe carrying a flow with ???23 mg/L dissolved CO2, into a second 11 m3 "harvest" tank. The research was conducted using separate groups of rainbow trout held at commercially relevant densities (40-60 kg/m3). The average weight of fish ranged from 0.15 to 1.3 kg during the various trials. In all trials that used a constant flow of low CO2 water (???23 mg/L) entering the growout tank from the harvest tank, approximately 80-90% of the fish swam from the growout tank, through the transfer pipe, and into the harvest tank after the CO2 concentration in the growout tank had exceeded 60 mg/L. The fish that remained in the growout tank stayed within the area of relatively low CO2 water at the entrance of the transfer pipe. However, the rate of fish transfer from the growout tank to the harvest tank was more than doubled when the diameter of the transfer pipe was increased from 203 to 406 mm. To consistently achieve fish transfer efficiencies of 99%, water flow rate through the fish transfer pipe had to be reduced to 10-20% of the original flow just before the conclusion of each trial. Reducing the flow of relatively low CO2 water near the end of each fish transfer event, restricted the zone of relatively low CO2 water about the entrance of the fish transfer pipe, and provided the stimulus for all but a few remaining fish to swim out of the growout tank. Results indicate that the CO2 avoidance technique can provide a convenient, efficient, more economical, and reduced labor approach for fish transfer, especially in applications using large and well mixed circular culture tanks. ?? 2007 Elsevier B.V. All rights reserved.

Aquacultural Engineering↗

USGS2016

Comparison of hydraulics and particle removal efficiencies in a mixed cell raceway and Burrows pond rearing system

We compared the hydrodynamics of replicate experimental mixed cell and replicate standard Burrows pond rearing systems at the Dworshak National Fish Hatchery, ID, in an effort to identify methods for improved solids removal. We measured and compared the hydraulic residence time, particle removal efficiency, and measures of velocity using several tools. Computational fluid dynamics was used first to characterize hydraulics in the proposed retrofit that included removal of the traditional Burrows pond dividing wall and establishment of four counter rotating cells with appropriate drains and inlet water jets. Hydraulic residence time was subsequently established in the four full scale test tanks using measures of conductivity of a salt tracer introduced into the systems both with and without fish present. Vertical and horizontal velocities were also measured with acoustic Doppler velocimetry in transects across each of the rearing systems. Finally, we introduced ABS sinking beads that simulated fish solids then followed the kinetics of their removal via the drains to establish relative purge rates. The mixed cell raceway provided higher mean velocities and a more uniform velocity distribution than did the Burrows pond. Vectors revealed well-defined, counter-rotating cells in the mixed cell raceway, and were likely contributing factors in achieving a relatively high particle removal efficiency-88.6% versus 8.0% during the test period. We speculate retrofits of rearing ponds to mixed cell systems will improve both the rearing environments for the fish and solids removal, improving the efficiency and bio-security of fish culture. We recommend further testing in hatchery production trials to evaluate fish physiology and growth.

Idaho↗

USGS2017

Performance and application of a fluidized bed limestone reactor designed for control of alkalinity, hardness and pH at the Warm Springs Regional Fisheries Center

Springs serving the Warm Springs Regional Fisheries Center, Warm Springs, Georgia, have pH, alkalinity, and hardness levels thatlie under the range required for successful fish propagation while free CO 2 is well above allowable targets. We evaluate a pretreatment process that exploits limestone’s (CaCO 3 ) ability to react away hydrogen ions (H + ) and carbon dioxide (CO 2 ) while increasing alkalinity (HCO 3 − ) and calcium (Ca2+) concentrations, i.e. CaCO 3 + H + ↔ HCO 3 − + Ca 2+ CaCO 3 + CO 2 + H 2 O ↔ Ca 2+ + 2HCO 3 − Limestone sand was tested in both pilot and full scale fluidized bed reactors (CycloBio®). We first established the bed expansion characteristics of three commercial limestone products then evaluated the effect of hydraulic flux and bed height on dissolution rate of a single selected product (Type A16 × 120). Pilot scale testing at 18C showed limestone dissolution rates were relatively insensitive to flux over the range 1.51–3.03 m 3 /min/m 2 but were sensitive (P < 0.001; R 2 = 0.881) to changes in bed height (BH, cm) over the range 83–165 cm following the relation: (Alkalinity, mg/L) = 123.51 − (3788.76 (BH)). Differences between filtered and non-filtered alkalinity were small(P > 0.05) demonstrating that limestone was present in the reactor effluent primarily in the form of dissolved Ca(HCO 3 ) 2 . Effluent alkalinity exceeded our target level of 50 mg/L under most operating conditions evaluated with typical pilot scale values falling within the range of 90–100 mg/L despite influent concentrations of about 4 mg/L. Concurrently, CO 2 fell from an average of 50.6 mg/L to 8.3 mg/L (90%), providing for an increase in pH from 5.27 to a mean of 7.71. The ability of the test reactor to provide changes in water chemistry variables that exceeded required changes allowed for a dilution ratio of 0.6. Here, alkalinity still exceeded 50 mg/L, the CO 2 concentration remained well below our limit of 20 mg/L (15.4 mg/L) and the pH was near neutral (7.17). Applying the dilution ratio of 0.6 in a full scale treatment plant at the site reduced by 40% the volume of spring water that is directed through each of three parallel reactors that combined react away 49,000 kg of limestone/yr.

Aquacultural Engineering↗

USGS2001

Mucous lysozyme levels in hatchery coho salmon (Oncorhynchus kisutch) and spring chinook salmon (O. tshawytscha) early in the parr-smolt transformation

Mucous lysozyme concentrations were determined in juvenile coho salmon (Oncorhynchus kisutch) and spring chinook salmon (O. tshawytscha) to establish reference levels during the time associated with the parr-smolt transformation. The first reported naris and vent mucous lysozyme levels are provided for spring chinook salmon and coho salmon. Naris mucous lysozyme levels ranged between 300 and 700 ??g ml-1, vent mucous lysozyme from 100 to 300 ??g ml-1, and skin mucous lysozyme levels were below 130 ??g ml-1. Lysozyme levels in the two species showed the same relationship with the highest levels in naris mucous, and the lowest in skin mucous. A seasonal decrease occurred in both species with a significant decrease in naris mucous lysozyme between February and March. Gill ATPase levels used to monitor smolt development during the same period did not reach ranges reported for smolts for either species during emigration. Identification of seasonal levels of lysozyme activity in mucous provides an alternative determination of developmental status prior to release of fish from the hatchery when salmonids are still undergoing the parr-smolt transformation. ?? 2001 Elsevier Science B.V.

Aquaculture↗

USGS2001

Oxytetracycline depletion from skin-on fillet tissue of coho salmon fed oxytetracycline medicated feed in freshwater at temperatures less than 9°C

Oxytetracycline (OTC) is a broad spectrum antibacterial agent approved in the USA for treating certain bacterial diseases in salmonids cultured in freshwater at temperatures greater than or equal to 9°C. This study was conducted to provide the information necessary to expand the OTC label to include treatment of diseased salmonids cultured in freshwater at temperatures below 9°C. The study was designed to treat juvenile coho salmon ( Oncorhynchus kisutch ) with OTC-medicated feed and determine the depletion of OTC from the skin-on fillet tissue. Oxytetracycline depletion was evaluated in juvenile coho salmon (weight range, 13–62 g) fed OTC-medicated feed at a rate of 88.2 mg OTC/kg body weight/day for 10 days. Pairs of skin-on fillets were taken from individual fish on days 4 and 10 during the treatment phase and on days 1, 4, 8, 14, and 19 during the depletion phase. Water temperatures during the study period ranged from 4.1°C to 8.5°C. The OTC concentrations in medicated feed and skin-on fillets were determined with high-performance liquid chromatography methods. The maximum mean OTC concentration in fillet tissue was 932 ng/g, 1 day after the last treatment and decreased to 32 ng/g 19 days after the last treatment. The log-linear loss of OTC from the fillet tissue was biphasic with a terminal phase half-life of 4.9 days.

Aquaculture↗

USGS2002

Practical application of disease resistance: A brook trout fishery selected for resistance to furunculosis

Selection is unwittingly influenced by nuances of fish culturists and adaptation of fish to intensive culture within artificial environments. When pathogens are present, susceptible individuals may be selectively eliminated from a population, accounting for inter-specific and intra-specific differences in susceptibility to disease. Biologists often intensify such selection to enhance resistance. Particularly important to this discourse is the selective breeding program initiated by the New York State Department of Environmental Conservation (Rome, NY, USA) to produce brown trout ( Salmo salar ) and brook trout ( Salvelinus fontinalis ) that are resistant to Aeromonas salmonicida . This program, specifically as it relates to brook trout, is reviewed throughout the current manuscript. In addition, we present a comparison between the performance of the Rome strain of brook trout to that of the Owhi strain of brook trout during a 17-month production cycle at the Ed Weed Fish Culture Station (Grand Isle, VT, USA) and after stocking into Vermont waters. The Owhi strain is used in recreational fisheries because it has good post-stocking survival, but these fish are sensitive to furunculosis. Our data indicated that the Rome strain had a food conversion rate of 1.3 that was slightly less than the 1.1 conversion rate of the Owhi brook trout. The growth rate measured as Monthly Temperature Units per inch (MTU/in.) among Rome brook trout (24.9 MTU/in.) was better than the Owhi brook trout (29.5 MTU/in.). Both the average length (23.6 cm) and weight (159.7 g) of individual Rome brook trout were superior to those of the Owhi strain (20.4 cm and 78.2 g, respectively). Just prior to stocking, survival within the hatchery was 84% among the Rome trout, but only 51% among the Owhi brook trout and mortality was attributed to a persistent epizootic of furunculosis. Microbiological assays indicated that the prevalence of A. salmonicida in dermal mucus attained equivalent levels within both strains of fish at different phases of the production cycle. The level of systemic infection, however, was regulated to a much greater extent by the Rome strain of brook trout throughout production. Our results indicated that the Rome brook trout strain satisfies management objectives for establishing an effective recreational brook trout fishery. Use of this strain also reduces management issues that complicate production when A. salmonicida is enzootic.

Vermont↗

USGS2002

Epidemiological investigation of infectious hematopoietic necrosis virus in salt water net-pen reared Atlantic salmon in British Columbia, Canada

An epidemiological study of infectious hematopoietic necrosis viral disease (IHN) in farmed Atlantic salmon in British Columbia was conducted to better understand the management of this disease. The study consisted of a descriptive retrospective investigation of 18 IHN outbreaks on farms between 1992 and 1996, and a prospective surveillance program for the viral disease, after an area management plan was implemented to reduce the viral load around farms and farm-to-farm spread of the virus. The crude cumulative mortality associated with IHNV in Atlantic salmon was high (average 47%), and outbreaks lasted 5.8 months on average. On the two farms where the virus was detected during the surveillance program, IHNV was confirmed in all pens within 1 month. On two of three sites where fish were kept on farms after the initial disease outbreak subsided, IHN reoccurred within 30 weeks. The presentation of IHNV on farms, the spatial and temporal patterns of the outbreaks between 1992 and 1996, and the genetic similarity between isolates collected from nine outbreaks spanning a 5-year period, all supported the plausibility of farm-to-farm spread of the virus. Furthermore, the marked decrease in the incidence rate of IHN in farmed Atlantic salmon after the implementation of an area-based management plan aimed at reducing farm-to-farm spread of the virus also supported this hypothesis. Although the source of IHNV for the index case was not determined in this study, secondary spread of the virus between farms via management practices, such as movement of fish, co-habiting naı̈ve fish with survivors of the viral disease, and movement of equipment, likely accounted for some farm outbreaks. This suggested that many cases of IHN may be preventable using good on-farm biosecurity.

Aquaculture↗

USGS2003

A simple analytical procedure to replace HPLC for monitoring treatment concentrations of chloramine-T on fish culture facilities

Concentrations of chloramine-T must be monitored during experimental treatments of fish when studying the effectiveness of the drug for controlling bacterial gill disease. A surrogate analytical method for analysis of chloramine-T to replace the existing high-performance liquid chromatography (HPLC) method is described. A surrogate method was needed because the existing HPLC method is expensive, requires a specialist to use, and is not generally available at fish hatcheries. Criteria for selection of a replacement method included ease of use, analysis time, cost, safety, sensitivity, accuracy, and precision. The most promising approach was to use the determination of chlorine concentrations as an indicator of chloramine-T. Of the currently available methods for analysis of chlorine, the DPD ( N , N -diethyl- p -phenylenediamine) colorimetric method best fit the established criteria. The surrogate method was evaluated under a variety of water quality conditions. Regression analysis of all DPD colorimetric analyses with the HPLC values produced a linear model ( Y =0.9602 X +0.1259) with an r 2 value of 0.9960. The average accuracy (percent recovery) of the DPD method relative to the HPLC method for the combined set of water quality data was 101.5%. The surrogate method was also evaluated with chloramine-T solutions that contained various concentrations of fish feed or selected densities of rainbow trout. When samples were analyzed within 2 h, the results of the surrogate method were consistent with those of the HPLC method. When samples with high concentrations of organic material were allowed to age more than 2 h before being analyzed, the DPD method seemed to be susceptible to interference, possibly from the development of other chloramine compounds. However, even after aging samples 6 h, the accuracy of the surrogate DPD method relative to the HPLC method was within the range of 80–120%. Based on the data comparing the two methods, the U.S. Food and Drug Administration has concluded that the DPD colorimetric method is appropriate to use to measure chloramine-T in water during pivotal efficacy trials designed to support the approval of chloramine-T for use in fish culture.

Aquaculture↗

USGS2003

Effects of various feed supplements containing fish protein hydrolysate or fish processing by-products on the innate immune functions of juvenile coho salmon (Oncorhynchus kisutch)

Immunomodulators administered to fish in the diet have been shown in some cases to enhance innate immune defense mechanisms. Recent studies have suggested that polypeptide fractions found in fish protein hydrolysates may stimulate factors in fish important for disease resistance. For the current study, groups of coho salmon were reared on practical feeds that contained either fish meal (Control diet), fish meal supplemented with cooked fish by-products, or fish meal supplemented with hydrolyzed fish protein alone, or with hydrolyzed fish protein and processed fish bones. For each diet group, three replicate tanks of fish were fed the experimental diets for 6 weeks. Morphometric measurements, and serologic and cellular assays were used to evaluate the general health and immunocompetence of fish in the various feed groups. Whereas the experimental diets had no effect on the morphometric and cellular measurements, fish fed cooked by-products had increased leucocrit levels and lower hematocrit levels than fish from the other feed groups. Innate cellular responses were increased in all feed groups after feeding the four experimental diets compared with pre-feed results. Subgroups of fish from each diet group were also challenged with Vibrio anguillarum (ca. 7.71 ?? 105 bacteria ml-1) at 15??C by immersion. No differences were found in survival among the various feed groups.

Aquaculture↗

USGS2003

Fin development in stream- and hatchery-reared Atlantic salmon

To determine the effect of development and environment on fin growth, we measured fin lengths of juvenile Atlantic salmon (Salmo salar) from two hatcheries (August, October and April-May), stream-reared fish (July and October) stocked as fry into two tributaries, and smelts from the main stem of the Connecticut River (May). For stream-reared parr, there was a linear relationship between the dorsal, caudal and anal fins with fork length, while the pectoral, pelvic and adipose fins exhibited a curvilinear relationship with fork length. Parr from a high gradient stream had larger caudal fins than fish from a low gradient stream, but other fins did not differ. Regression lines for the fins of stream-reared smelts were all linear when fin length was regressed against fork length. Stream-reared parr had larger pectoral, pelvic and anal fins than smolts of similar size while dorsal and caudal fin lengths did not differ. Regression equations formulated using the fins of stream-reared parr were used to calculate the percent difference (100 x observed fin length/expected) in fin lengths between stream- and hatchery-reared parr. The pelvic, adipose, caudal and anal fins of hatchery-reared parr showed no signs of degeneration by the first sampling period 7 months after hatching, whereas degeneration in the pectoral (13-20%) and dorsal (15-18%) fins was evident at this time. By the end of the study, degeneration was present in every fin except the adipose, with the pectoral (35-65%) and dorsal (32-58%) fins exhibiting the greatest amount of fin loss. All fins of hatchery-reared parr became shorter with time. There were minor differences in fin degeneration among parr from the two hatcheries, but the overall pattern of decreasing fin size was similar, indicating a common cause of fin degeneration. Comparison of stream- and hatchery-reared fish is a valuable means of determining the impact of captive environments on fin growth.

Aquaculture↗

USGS1997

The effects of experimental starter diets with different levels of soybean or menhaden oil on red drum (Sciaenops ocellatus)

Red drum reared from captive-spawned eggs were used in a 2 × 4 factorial experiment comparing eight diets with soybean oil (SBO) or menhaden oil (MHO) added to a basal diet (about 3.4% lipid from practical ingredients) at 1.5, 5.2, 9.0, or 12.7%. Triplicate groups of 20 early juveniles (mean 0.4 g) were stocked in 1000 litre fiberglass tanks supplied with filtered estuarine water (17–26 °C, mean 22 °C; 15–35‰) and hand fed twice a day to apparent satiation for 56 days. The fish (range 0.3–9.4 g) appeared to utilize up to 1.5–5.2% dietary SBO (in 5.4–8.7% total lipid). With 0.67% EPA + DHA (eicosapentaenoic and docosahexaenoic acids) in the basal diet, no EFA-deficiency signs were observed. Dietary MHO was utilized up to 12.7%, but fish fed diets with more than 1.5% SBO had lower growth rates and increased feed conversion ratios (especially with 9.0 and 12.7% SBO). Diets containing 1.5% SBO or MHO produced the leanest fish (70.5–71.6% protein, 13.0–13.1% lipid, of whole body). Diets containing 9.0 and 12.7% MHO produced the fattest fish (64.5–66.0% protein and 19.1–19.9% lipid). Percent liver lipid (wet) was highest for fish fed diets containing 5.2% SBO (41.4%), 9.0% MHO (36.5%), and 12.7% MHO (35.4%), and lowest with 1.5% MHO (24.0%). Considering the good survival, absence of disease, and excellent general health, this fatty liver condition did not appear to have short-term adverse effects. All fish in the study had fatty livers to some degree, and their liver histological features differed from those of wild fish. Liver lipid reserves might confer some survival advantage to fish released for stock enhancement if the reserves are used during their transition from cultured to wild status. However, if the hepatocyte changes we observed are not reversible, long-term detrimental effects on liver function are possible.

Aquaculture↗

USGS1998

Seasonal differences in plasma cortisol and gill corticosteroid receptors in upper and lower mode juvenile Atlantic salmon

Circulating plasma cortisol and gill corticosteroid receptors (CR) have been observed to change seasonally in conjunction with smolting in Atlantic salmon. To differentiate whether these changes are seasonal or ontogenic, juvenile Atlantic salmon parr were separated by size into upper (UM) and lower mode (LM) in September. At monthly intervals, the fish were sampled for plasma cortisol, gill Na + K + ATPase activity and CR abundance ( B max ) and dissociation constant ( k D ). UM were significantly larger than LM, and showed the silver appearance characteristic of smolts in April and May. Gill Na + K + ATPase activity of UM fish increased 6-fold during the spring; LM fish increased 1.5-fold. Plasma cortisol levels increased significantly (10-fold) in UM fish in May, but not in LM fish. Gill CR B max increased 5-fold over the duration of the study in both groups. CR k D was lowest in October and highest in May; a 1.8- and 2-fold increase in LM and UM, respectively. There were no significant differences in gill CR B max and k D between the two groups during the study, except in May, when k D was significantly greater and B max lower in UM than LM. Peak levels of gill Na + K + ATPase activity occur coincident with an increase in plasma cortisol concentration. Seasonal increases in CR B max and k D are similar in UM and LM fish and occur independent of smolting in juvenile Atlantic salmon. In UM fish, plasma cortisol increases in spring are concurrent with increased smolt characteristics.

Aquaculture↗